1. Field
One embodiment of the invention relates to a cooling device in which liquid coolant is circulated for cooling a heat generating element in an electronic apparatus.
2. Description of the Related Art
Regarding a CPU or the like used in an electronic apparatus such as a portable computer, the amount of heat generated during operations is increasing, accompanying with faster speed operation and more multifunctional device. If the temperature of the CPU becomes too high, the CPU processing speed may decrease and there may be errors in the CPU operation.
In recent years, in order to increase cooling performance for the CPU, electronic apparatuses have been implemented with a so-called liquid cooling type cooling device in which liquid coolant (hereinafter “coolant”) such as antifreeze or water, is circulated. Heat generated by the CPU is radiated outside the electronic apparatus by using the coolant having a specific heat which is much higher that air.
The above-described conventional cooling device comprises a heat receiving portion thermally connected to the CPU, a heat radiation portion which radiates a heat of the CPU, a circulation passage which makes connection between the heat reception portion and the heat radiation portion, and a pump which circulates a liquid coolant along the circulation passage.
The liquid coolant absorbs the heat from the CPU by heat exchange at the heat reception portion. The heated liquid coolant is sent to the heat radiation portion through the circulation passage and radiates the heat of the CPU in a course of passing the heat radiation portion. The liquid coolant cooled at the heat radiation portion returns to the heat reception portion through the circulation passage and absorbs the heat of the CPU again. By circulation of the liquid coolant, the heats of the CPU are sequentially transferred to the heat radiation portion, from which the transferred heats are radiated outside of a portable computer.
U.S. Pat. No. 6,519,147 discloses an electronic apparatus with this type of cooling device.
In the meantime, a conventional cooling device is provided with a reserve tank in the middle of a circulation passage. The reserve tank is intended to supplement an evaporation component of the liquid coolant and reserves a predetermined amount of the liquid coolant. Further, the reserve tank has an injection port. The injection port is available for use in injecting the liquid coolant into the circulation passage and is closed by a removable cap except for a liquid coolant injection mode.
According to such the conventional cooling device, after a heat reception portion has been connected to a heat radiation portion via a circulation passage, a liquid coolant is injected from an injection port of a reserve tank to a circulation passage. However, in a state in which piping of the circulation passage has been completed, a sealed space in which the inside of the circulation passage is shielded from the outside is provided. Therefore, even if the liquid coolant is injected from the injection port, the flow of the liquid coolant is prevented by the air which remains inside of the circulation passage or inside of the pump, and a long time is required until the liquid coolant has reached the pump.
As a result, even if an attempt is made to drive the pump and transfer the liquid coolant to the circulation passage, a wait time is extended until the pump has functioned efficiently. In other words, it takes long to fill the circulation passage with the liquid coolant.